312
T. Soomere
Fig. 9.17 Ratio of net and bulk transport (colour scale) for 1987–1991 (left) and for 1991 (right)
(Soomere et al. 2011a)
port direction varies: in 1987 it was to the north whilst in 1988 it was to the south,
with a typical speed up to 0.05 m/s, that is, about half of that for the meridional
transport.
Several rapid pathways of net transport revealed substantial excursions of the
flow. The ratio of net and bulk transport additionally showed how straight the motions of the tracers are. This measure of the variability in the current direction allowed in addition to distinguish the areas hosting unidirectional currents from eddydominated regions. Its reasonable calculation required time windows much longer
than the typical turnover time of eddies.
The relevant distributions found using t W = 15 days in 1987–1991 (Soomere
et al. 2011a) highlighted coastal currents in the SE Gulf of Finland and to a lesser
extent the runoff of the River Neva (Fig. 9.17). This ratio had limited interannual
variability but exhibited substantial spatial variations during different seasons. Interestingly, the regions of high values in calm seasons (Soomere et al. 2011a, Fig. 12)
matched the location of the area of overall high persistency of motions in the subsurface layer (Andrejev et al. 2004a).
9.5 Concluding Remarks
This chapter presented a selection of outcomes from test simulations developed to
understand the role of the basic time scales, parameters and options of the discretization of the inverse problem of environmental management. The obtained knowledge
and established sensible parameters and options serve as a cornerstone of the solutions described in the next chapter. The key message is a demonstration of the ability
of the systematic use of Lagrangian trajectories to reveal usually concealed features
of the surface flow. Examples using this technique indicate the potential richness
of semi-persistent structures in water bodies with complicated dynamics such as
the Gulf of Finland. These patterns are normally hidden in the classical Eulerian
representation. Some of them evidently cannot be extracted from a straightforward
analysis of the Eulerian velocity fields at all.
The presence of relatively intense mostly meridional transport pathways in some
seasons and sections of the Gulf of Finland is highly intriguing. Although they do
not occur every year, their existence is of major importance in the context of the
T. Soomere
Fig. 9.17 Ratio of net and bulk transport (colour scale) for 1987–1991 (left) and for 1991 (right)
(Soomere et al. 2011a)
port direction varies: in 1987 it was to the north whilst in 1988 it was to the south,
with a typical speed up to 0.05 m/s, that is, about half of that for the meridional
transport.
Several rapid pathways of net transport revealed substantial excursions of the
flow. The ratio of net and bulk transport additionally showed how straight the motions of the tracers are. This measure of the variability in the current direction allowed in addition to distinguish the areas hosting unidirectional currents from eddydominated regions. Its reasonable calculation required time windows much longer
than the typical turnover time of eddies.
The relevant distributions found using t W = 15 days in 1987–1991 (Soomere
et al. 2011a) highlighted coastal currents in the SE Gulf of Finland and to a lesser
extent the runoff of the River Neva (Fig. 9.17). This ratio had limited interannual
variability but exhibited substantial spatial variations during different seasons. Interestingly, the regions of high values in calm seasons (Soomere et al. 2011a, Fig. 12)
matched the location of the area of overall high persistency of motions in the subsurface layer (Andrejev et al. 2004a).
9.5 Concluding Remarks
This chapter presented a selection of outcomes from test simulations developed to
understand the role of the basic time scales, parameters and options of the discretization of the inverse problem of environmental management. The obtained knowledge
and established sensible parameters and options serve as a cornerstone of the solutions described in the next chapter. The key message is a demonstration of the ability
of the systematic use of Lagrangian trajectories to reveal usually concealed features
of the surface flow. Examples using this technique indicate the potential richness
of semi-persistent structures in water bodies with complicated dynamics such as
the Gulf of Finland. These patterns are normally hidden in the classical Eulerian
representation. Some of them evidently cannot be extracted from a straightforward
analysis of the Eulerian velocity fields at all.
The presence of relatively intense mostly meridional transport pathways in some
seasons and sections of the Gulf of Finland is highly intriguing. Although they do
not occur every year, their existence is of major importance in the context of the